Maps a function over lists or vectors in parallel.

Uses the parallelization mode and the other options specified in parallelStart().

Libraries and source file can be initialized on slaves with parallelLibrary() and parallelSource().

Large objects can be separately exported via parallelExport(), they can be simply used under their exported name in slave body code.

Regarding error handling, see the argument impute.error.

parallelMap(
  fun,
  ...,
  more.args = list(),
  simplify = FALSE,
  use.names = FALSE,
  impute.error = NULL,
  level = NA_character_,
  show.info = NA
)

Arguments

fun	function Function to map over `...`.
...	(any) Arguments to vectorize over (list or vector).
more.args	list A list of other arguments passed to `fun`. Default is empty list.
simplify	(`logical(1)`) Should the result be simplified? See simplify2array. If `TRUE`, `simplify2array(higher = TRUE)` will be called on the result object. Default is `FALSE`.
use.names	(`logical(1)`) Should result be named? Use names if the first `...` argument has names, or if it is a character vector, use that character vector as the names.
impute.error	(`NULL` \| `function(x)`) This argument can be used for improved error handling. `NULL` means that, if an exception is generated on one of the slaves, it is also thrown on the master. Usually all slave jobs will have to terminate until this exception on the master can be thrown. If you pass a constant value or a function, all jobs are guaranteed to return a result object, without generating an exception on the master for slave errors. In case of an error, this is a `simpleError()` object containing the error message. If you passed a constant object, the error-objects will be substituted with this object. If you passed a function, it will be used to operate on these error-objects (it will ONLY be applied to the error results). For example, using `identity` would keep and return the `simpleError`-object, or `function(x) 99` would impute a constant value (which could be achieved more easily by simply passing `99`). Default is `NULL`.
level	(`character(1)`) If a (non-missing) level is specified in `parallelStart()`, this call is only parallelized if the level specified here matches. Useful if this function is used in a package. Default is `NA`.
show.info	(`logical(1)`) Verbose output on console? Can be used to override setting from options / `parallelStart()`. Default is NA which means no overriding.

Value

Result.

Examples

parallelStart()
parallelMap(identity, 1:2)
#> [[1]]
#> [1] 1
#> 
#> [[2]]
#> [1] 2
#> 
parallelStop()